Epothilones are a microtubule stabilizing compounds structurally distinct from Paclitaxel (Taxol(r)). Since epothilones are not a substrate for P-glycoprotein, are effective against Taxol-resistant cell lines, and are more soluble than Taxol, they are considered to be likely successors to Taxol. Unfortunately, the producing organism, Sorangium cellulosum, grows very slowly and produces only about 20 mg/L of epothilones. Furthermore, chemical synthesis of epothilones is impractical due to the complexity of the synthetic process. Overexpression of the epothilone gene cluster in Streptomyces has been accomplished, but yields of only 50-100 microgram/liter were obtained. In the Pl's possession is a unique collection of S. cellulosum assembled from the 1950's through the early 1970's by Dr. John Peterson, a notable expert on S. cellulosum. Researchers worldwide acknowledge the uniqueness and scientific potential of this collection which currently consists of approximately 400 uncharacterized strains. In lieu of the promise epothilones hold as potential cancer therapeutic agents, and the possession of a historic S. cellulosum culture collection assembled by a noted expert, the broad, long-term goal of this project is to obtain epothilones in quantities suitable for evaluation on the chemical and clinical levels. To accomplish this goal, the specific aims of this project are: Aim 1) To screen a unique collection of approximately 400 uncharacterized strains of S. cellulosum assembled by Dr. John Peterson for production of epothilones; Aim 2) To investigate alternate growth conditions for S. cellulosum leading to increased production of epothilones, and Aim 3) To perform random mutagenesis on wild-type organisms to obtain overproducers of epothilone.